KARKAMIS: A group allied to Kurdish-backed Syrian Democratic Forces (SDF) said it was bombarded by Turkish warplanes on Saturday, after Turkey's military launched an incursion this week into northern Syria against both Islamic State and Kurdish forces.

Turkish military sources said planes had hit an ammunition store south of Jarablus, but they did not give details.

If the jets struck targets linked to the Kurdish-aligned group, it would signal Turkey's action against Kurdish-backed forces in Syria was being ratcheted up a notch.

The Jarablus Military Council, a group that is part of the Kurdish-backed SDF, said the jets hit a village south of the strategic town of Jarablus, causing civilian casualties. It called the action "a dangerous escalation".

A Reuters witness in Karkamis, a Turkish town on the other side of the border from Syria's Jarablus, saw warplanes flying from Turkish air space early on Saturday into Syria and then heard several blasts. The identity of the planes was not clear.

Syrian rebels backed by Turkish special forces, tanks and warplanes entered Jarablus this week, seizing the frontier town that had been an Islamic State stronghold. The rebel force backed by Turkey were largely Arab and Turkmen.

The Turkish campaign pre-empted action by Kurdish-backed forces which had sought to get to Jarablus first.

Turkish President Tayyip Erdogan and other senior officials have made clear that the incursion is as much about pushing away Islamic State as it is about preventing Kurdish forces filling the void left as the Islamists withdraw.

Turkey wants to stop Kurdish forces gaining control of a continuous stretch of territory along its southern border, which Ankara fears could be used to support the Kurdish militant group PKK that is fighting an insurgency on Turkish soil.

Turkish-backed Syrian rebels have extended their control beyond Jarablus, seizing five nearby villages from Islamic State, Turkish security sources said. The Turkish Red Crescent has distributed food in Jarablus since Friday, the sources said.

RIVALRIES AND ALLIANCES

The Jarablus Military Council said the village of al-Amarna, which lies a few km south of Jarablus, was hit by the warplanes. In response to the Turkish strike, it said: "If they do not attack our forces, then we will keep the border strip secure."

The newly formed Jarablus Military Council has said it was made up of people from the area with the aim of capturing the town and the surrounding region from Islamic State militants. However, the Turkish-backed rebels seized Jarablus first.

The Jarablus Military Council has aligned itself with the SDF, which encompasses several militias including Arabs and the Kurdish YPG group.

The SDF alliance is backed by the United States, putting Ankara at odds with NATO ally Washington in the engagement in Syria, where a multi-faceted conflict has raged for five years. A complex web of rivalries and alliances has emerged from what began with an uprising against Syrian President Bashar al Assad, drawing in world powers and regional states.

On Thursday, a day after Turkey began its cross-border offensive, Turkish troops fired on U.S.-backed YPG forces, which is part of the SDF. Turkey's state news agency described that salvo as warning shots. The use of Turkish warplanes against an SDF-aligned group would point to tougher action.

A Reuters witness in Karkamis heard blasts and smoke rising from the nearby Syrian village of Kivircik.

Several militias under the SDF banner pledged support to Jarablus Military Council after it reported the Turkish bombing.

The Northern Sun Battalion, an SDF faction, said in a statement it was heading to "Jarablus fronts" to help the council against "threats made by factions belonging to Turkey".

Tension has mounted in Syria's Aleppo region in the past year between the U.S-backed Kurdish YPG force and its allies on one hand and Turkish-backed rebel groups on the other. The two sides have clashed on several occasions.